Implementation of the effect of urease inhibitor on ammonia emissions following urea-based fertilizer application at a Zea mays field in central Illinois: A study with SURFATM-NH ₃ model

Agriculture is the main source of ammonia (NH ₃ ) emissions in the atmosphere. NH ₃ is precursor to secondary fine particulate matter, which is of concern for its impacts on health and visibility. There are a limited number of field measurements of NH ₃ emissions from fertilizer application in the US, and this limits our understanding of the importance of individual NH ₃ source and sink processes in controlling timing and magnitude of NH ₃ emissions. In this study, a new parameterization of the effect of urease inhibitor on NH ₃ emissions from urea-based fertilizer was developed on the basis of experimental results found in the literature. This parameterization was combined with an existing operational parameterization of soil and stomatal emission potentials (Γ _g , Γ _s ) and was implemented in a surface-atmosphere transfer model for NH ₃ (SURFATM-NH ₃ ) in order to evaluate the bi-directional fluxes of NH ₃ at the field scale. The model was evaluated with field measurements obtained by the flux-gradient (FG) and relaxed eddy accumulation (REA) methods in a fertilized corn field in central Illinois. By integrating the effect of urease inhibitor, the timing of the highest NH ₃ emission peak was successfully predicted and its magnitude was close to that measured (predicted 2106 ng m ⁻² s ⁻¹ , measured by FG 2312 ± 582 ng m ⁻² s ⁻¹ ). Based on the model results, urease inhibitor has a considerable effect on the dynamics and order of magnitude of NH ₃ fluxes. Furthermore, the model simulated the inhibiting action of N-(n-butyl) thiophosphoric (nBTPT) and suggests that it can reduce NH ₃ volatilization by 32%. The model also successfully predicted environmental parameters, such as soil temperature. Finally, this new version of SURFATM-NH ₃ is a valuable tool to estimate the NH ₃ bi-directional fluxes at the field scale, which describes dynamic modeling of Γ _s and Γ _g by taking into account the effect of urease inhibitor which is commonly used in the US to improve the efficiency of urea fertilizers.